Tow opening



July 4, 1967 WATSON 3,328,850

TOW OPENING Filed July 13/1964 Q a Q INVENTOR.

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Age/m- T United States Patent 3,328,850 TOW OPENING George A. Watson, Charlotte, N.C., assignor to Celanese Corporation, a corporation of Delaware Filed July 13, 1964, Ser. No. 382,018 9 Claims. (Cl. 19-65) This invention relates to the opening of crimped strands of continuous filamentary materials.

The use of patterned rolls for the opening of crimped strands, such as crimped tows made up of a large number of continuous filaments with the crimps in registry, is known to the art. Examples of processes of this type are found in US Patent 3,032,829 and Canadian Patent 674,101 (corresponding to US. application 151,900 of Nov. 13, 1961 now US. Patent 156,016).The resulting opened tows are suitable for the production of diverse items such as cigarette filters, upholstery piping and wicks.

It is an object of this invention to improve on the patterned roll opening processes so as to obtain tows which are more uniformly opened and which yield superior finished products.

Other objects of this invention will be apparent from the following detailed description and claims. In this description and claims, all proportions are by weight unless otherwise indicated.

In accordance with one aspect of this invention, a crimped tow or other continuous multifilament strand is passed through an opening zone in which it is subjected to the action of patterned rolls which grip and release the filaments differentially, preferably by acting on certain spaced groups of filaments in such a manner that there is a continual change in the selection of the particular filaments making up these spaced groups during the passage of the tow between the rolls, so that different filaments are gripped and released at different times, and the tow is passed in sliding contact over an electrical insulating surface in said opening Zone. It is found that, when such sliding contact is provided, the tow tends to spread much more easily and uniformly, with much less tendency to form folds in subsequent processing, and is particularly suitable for subsequent air spreading in the manner described in my copending application (Ser. No. 382,263), filed on even date herewith and entitled Webs, whose disclosure is hereby incorporated by reference.

The drawing illustrates one invention, wherein:

The figure is a schematic elevational view of one form of a tow opening apparatus.

Referring now more particularly to the drawing, there is shown a bale 11 of tow 12 made up of crimped filaments such as polyester (e.g. polyethylene terephthalate) or cellulose acetate. The tow is generally in the form of a relatively flat band, having ridges across substantial portions of its width, such ridges being formed by the aligned crests and troughs of crimps of adjacent filaments. The band of tow 12 is drawn upwardly from the bale 11 over a series of stationary tensioning bars 13, and 14 and then through a banding jet 17 which spreads it laterally several fold without eflec-ting any significant de-registry of the aligned crimps. In the banding jet the tow band passes through a confined zone, between two generally parallel walls 18, 19, where it is subjected across its whole width to one or more streams of air issuing from a slot in wall 18. From the banding jet 17 the tow passes under a guide bar 21, to the nips formed between a driven smooth rubber roll 22 and a grounded threaded steel roll 23. The movement of these rolls pulls the tow under slight tension over the preferred form of the tensioning bars 13, and 14 and through the banding jet 17.

From the nip of rolls 22, 23 the tow passes to the nip of a second pair of rolls, comprising driven smooth rubber roll 24 and threaded steel roll 26, being deflected in the reach between said rolls by passing under a deflecting guide which may, for example, be a grounded angle bar 27 made of a conducting material such as aluminum extending across the full width of the tow. The tow-contacting edge of the bar 27 is so positioned that the tow is brought into sliding contact with the surface of the rubber roll 24, which is moving faster than the tow as a whole.

In the particular embodiment shown in the drawing, the nip between rolls 22, 23 and the nip between rolls 24, 26 is in a plane tangent to all said rolls, while the straight line joining the tow-engaging edge of the guide bar 27 and the nip of rolls 24, 26 intersects a substantial portion of the roll 24, and the tow slides, relative to the moving surface of roll 24, about A to inch before reaching said nip.

The rolls 24, 26 are operated at a peripheral speed appreciably greater than that of the upstream rolls 22 and 23. This increase in speed is not sufficient to place the tow under substantial tension; the crimp in the filaments is still noticeable in the tow passing between the pairs of rolls, and the tow can be manually deflected out of its normal straight path with ease. The higher speed of the downstream rolls 24, 26 is preferably just suflicient to avoid the tendency for slack to develop in the tow, which occurs when all the rolls are operated at the same speed and which, if permitted to continue without correction, may cause the tow to lap around the rolls, interrupting the processing. The downstream rolls 24, 26 may, for example, be operated at a peripheral speed in the range of about 1% to 1% times the speed of the upstream rolls 22, 23, preferably in the range of about 1.3 to 1.5 times the upstream roll speed; the exact value for best results will depend on the type of tow and the configuration of the rolls.

After leaving the nip between the rolls 24 and 26, the tow passes through air spreader 28 where it is exposed, in a confined zone such as a wide slot to the'action of air streams across its whole width, which spreads the tow to a wider and thinner band. The tow is pulled through the spreader 28 by the action of a pair of feed rolls 29, 31, driven at a speed just sufiicient to keep the tow passing to said rolls from substantial sagging in its path from rolls 24, 26. The tow passes in an S-configuration about the rolls 29, 31, travelling about around the top feed roll 29, which is preferably rubber-surfaced, then through the nip between rolls 29 and 31 and then about 180 around the lower feed roll 31, which may be a grounded steel-surfaced roll.

From the rolls 29, 31, the tow passes to a second air spreader 32, which is like spreader 28 but wider, where the tow band is spread still further, being forwarded through said spreader 32 by a set of rolls 33, 34. The operation in this stage of spreading is like that in the previous stage, except that the Width of the tow band is greater. As shown in FIG. 1 of the drawing, the tow band leaving the lower feed roll 31 makes a shallow catenary in its passage to the banding jet 32, which is mounted with its confined zone 36 horizontal and at a level lower than that of the bottom of feed roll 31. For example, the entrance to the tow passage 36 may be spaced 12 inches below and 36 inches (measured horizontally) beyond the bottom of feed roll 31. In the catenary the tow preferably does not sag below the level of the passage 36.

It is found that when the deflector bar 27 is employed, the filaments in the tow spread apart much more easily, the production of a more uniform spread band of tow is facilitated, and the tow does not tend to form folds in the spreader 28 (which folds may be carried downstream to the next stage resulting in the formation of a non-uniform spread product). It is believed that these effects may be due in part to the electrification of portions of the tow band by their sliding contact with the rubber surface of roll 24, despite the contact of portions of said tow band with the grounded conductive surfaced rolls 26 and 31.

It will be observed that these grounded rolls do not make contact with all the filaments of the band at any one time; thus, only the high portions or threads of roll 26 are in pressing contact with varyingly selected filaments of the tow hand. Also, some of the filaments will be insulated from the roll 31 by other filaments in contact with said roll. It will also be observed that the roll 31 engages the same side of the tow as the roll 26.

When the deflector bar 27 is used, the tow shows a tendency to bloom and to become thicker, on leaving the rolls 24, 26, presumably because of electrostatic repulsion of charged filaments. This three-dimensional blooming is controlled and utilized by the movement of the tow through the shallow horizontal confined zone 37 of the spreader 28, which zone, like the corresponding zone 36 of spreader 32 may, for example, have a depth on the order of about inch and a length (in the direction of the movement of the tow) of about 4 inches. The width of the tow hand increases uniformly from the nip of rolls 24, 26 to the exit of spreader 28, then remains substantially constant, then increases uniformly from the bottom of roll 31 to the exit of spreader 32 and continues at the same width from the spreader 32 to the roll 33.

The spread tow may be used for the production of batting, as by rolling or folding it on itself, if desired, followed by needling of the resulting bad, and the batting may be used for the stufling of such articles as pillows or upholstery. The spread tow may also be laminated to other materials such as paper, by any suitable adhesive, and thus serve to reinforce the paper while giving the paper a desirable soft surface. The opened tow may also be condensed to form a cigarette filter rod, with or without the previous application of plasticizer in known manner.

In accordance with another aspect of this invention, it has been found that the spreading action is enhanced when the tow fed to the patterned roll opening zone carries a hydrophobic silicone finish substantially free of antistatic agents. Preferably there is a tough, flexible, hydrophobic film of silicone resin around each individual fiber. The silicone is desirably applied to the filaments during their early stages of processing and before the band of tow is crimped. This may be done conveniently by passing the filaments through an aqueous emulsion of a relatively low molecular weight curable liquid silicone prior to the step of crimping the filaments and, in the case of materials which, like polyethylene terephthalate, must be drawn to develop desirable tenacity and resistance to elongation, prior to the drawing operation.

A suitable silicone is readily made, for example, from the hydrolysis of a major portion of an alkyl dichlorohydrogen silane and a minor portion of a dialkyl dichlorosilane. If desired, there may also be incorporated a small amount of trialkyl chlorosilane (as a chain terminator) and a small amount of alkyltrichlorosilane (to promote preliminary cross-linking). All the alkyl groups are preferably methyl groups. The use of these starting reactants results in a relatively fluid silicone containing a major portion of methylhydrogenpolysiloxane and a minor portion of dimethylpolysiloxane.

The polymeric silicone, after it has been emulsified and the emulsion applied to a filamentary material, can then be catalytically oxidized or cured so that the silane hydrogens are converted to additional siloxane oxygen bridges, to further cross-link the silicone. The resultant cross-linked polymeric product is tough, hydrophobic, and

highly lubricating; forming a flexible film around the surface of each filament.

It is convenient to first emulsify the silicone so as to form an aqueous emulsion of paste-like consistency. Any of the conventional silicone emulsifying agents, e.g. trimethylnonyl ether, can be used. The average particle size of the silicone polymer in this paste emulsion is generally from about 1 to 8 microns, and typically is about 5 microns. This paste is then incorporated into the finishing bath, along with catalyst. The catalyst compound used to promote further cross-linking of the silicone is of the conventional type used for silicone curing and generally is an organometallo compound or mixture thereof, and is typically an organometall-o salt. Generally the metal portion of such catalyst compound is zinc, tin, aluminum, zirconium, or the like. Suitable catalysts include zinc acetate, aluminum octoate, organic titanates, and mixtures thereof. As stated previously, such catalyst promotes oxidation of the silane hydrogens to produce additional siloxane oxygen linkages and thereby promote further crosslinking of the silicone polymer.

Generally the catalyst is maintained separately from the silicone emulsion until the finishing bath is to be prepared, and desirably is added as the last component to the finishing bath.

Desirably the weight ratio of silicone to metal catalyst is from about 8 to l to about 1 to l. A more preferred range is from about 5 to 1 to about 3 to 1. The aqueous composition applied to the filaments may contain, for example, 1 to 5% of the silicone.

The proportion of silicone on the filaments is advantageously less than 1%, preferably in the range of about 0.2 to 0.5% based on the weight of the filaments.

The crimping of the filaments carrying the silicone finish is advantageously carried out in a stuifer crimper, which may be of the standard stuifing box type in which the tow is forced into a narrow confined zone, thus folding the filaments back and forth on themselves in their passage through said zone. The tow in the crimper may carry a wet film of the aqueous uncured silicone finishing composition, which may be subsequently cured by heat treatment of the crimped tow while the latter is maintained in a relaxed condition, e.g. at a temperature above C., for example -180 C. Curing of the silicone may also be effected prior to crimping, as by passing the filaments carrying the uncured silicone finish through a heated drawing zone.

The following example is given to illustrate this invention further.

Example A band of tow, having a total denier of 100,000, comprising 5 d.p.f. filaments made of cellulose acetate, having 12 crimps per inch and carrying A% of a cured silicone coating, was passed through the apparatus shown in FIG. 1. In this example, the diameters of all the rolls 22, 23, 24, 26 were 6% inches, the roll 22 was driven at a peripheral speed of 41 feet per minute, the roll 24 at 57 feet per minute, the roll 31 at 43 feet per minute and the roll 34 at 45 feet per minute. The rolls 23, 26, 29 and 33 were spring-pressed towards the lower rolls 22, 24, 31 and 34 respectively, and were thus driven by contact with the tow moving over said lower rolls. Rolls 22 and 24 were both surfaced with rubber having a hardness of '70 durometer, A scale (Carotex B"). Each of rolls 23 and 26 had opposite helical threads, of 14 turns per inch cut about A inch deep into its outer surface, from the center of each roll to its end. The distance between the nip of rolls 22 and 23 and the nip of rolls 24, 26 was 20 inches and the deflector was mounted with its tow-engaging edge inch below the straight line joining said nips and 2 inches upstream of the nip of rolls 24, 26, so that the tow was in contact with the rubber-covered roll 24 over an angle of 23, equal to a distance of 1 inches before reaching the nip. Taking the speeds of the tow filaments, having about 3 and roll 24 into account, the sliding movement of the tow relative to the rubber surface of said roll extends for inch. The tow, which is spread to a width of about 8 inches at the banding jet 17 is spread to a width of 24 inches at the jet 28 and 50 inches at the jet 32, and may then be rolled or folded on itself to produce a batting for use in stufiing pillows, upholstery, insulation for clothing, etc.

While the invention has thus far found its greatest utility with respect to tows whose filaments are of polyethylene terephthalate or of cellulose acetate (of the usual acetyl content, e.g. about 54-55% calculated as acetic acid). It will be understood that it is within the broad scope of the invention to carry it out with other tows, such as those made of other polyesters (e.g. the polyesters of terephthalic acid and other glycols such as dimethylol cyclohexane), linear super polyamides (such as nylon 6 or nylon 66), polyacrylonitrile and copolymers of acrylonitrile, olefenic polymers and copolymers, e.g. isotactic polypropylene, other organic derivatives of cellulose such as esters and/or ethers of cellulose, for example cellulose propionate and cellulose acetate propionate or the like, highly esterified cellulose containing less than 0.29 free hydroxyl groups per anhydroglucose unit such as cellulose triacetate, rayon (regenerated cellulose). The number of filaments of the starting tow can vary within wide limits and may range up to as high as 1,000,000, with a denier per filament as high as 25, e.g. 1 to 20. The number of crimps per inch of tow may range up to as high as about 80, but for most end products to be described herein about 3 to 50, preferably about 3 to 20 crimps per inch of starting tow are found sufficient.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of this invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In the process in which a band of a plurality of continuous crimped filaments having crimps in registry is opened by passing said band through an opening zone in which said band is subjected to the action of a patterned roll to deregister said crimps through relative movement of said filaments under the influence of said patterned roll, the improvement which comprises passing said band in said zone in sliding contact over an electrically insulating surface.

2. Process as set forth in claim 1 in which said filaments carry a silicone finish substantially free of antistatic agents.

3. In the process in which a band of a crimped tow comprising about 500 to 1,000,000 continuous crimped to 80 crimps per inch and having crimps in registry, is opened and deregistered by passing it to the nip of a pair of rolls, one of which has a smooth rubbery insulating surface the other of which has a grooved surface, said rolls moving at a peripheral speed faster than the speed of said tow, the improvement which comprises feeding said tow to said nip so that the tow makes sliding engagement with about M4 to inch of said moving smooth surface at a substantially constant angle substantially before it engages said nip.

4. In apparatus for the Opening of tow, said apparatus including an opening zone having a pair of feed rolls adapted to be driven at a controlled speed, and a second pair of rolls for receiving a tow band from the firstmentioned pair of rolls and adapted to be driven at a peripheral speed greater than that of said first-mentioned pair, one of the rolls of said second pair of rolls being grooved circumferentially, the improvement which comprises providing the other roll of said second pair of rolls with a smooth electrically insulating surface and providing means for bringing said band in said zone into sliding contact with said electrically insulating surface which comprises stationary guide bar means in said zone so positioned that the straight line from said guide bar means to the nip of said second pair of rolls intersects a portion of said smooth surfaced roll so that the tow is in sliding engagement with a substantially constant arc of the moving smooth surfaces of said roll substantially before it passes through said nip.

5. Apparatus as set forth in claim 4 in which said grooves of said grooved roll run at an acute angle to the axis of said grooved roll and the filaments are only gripped between the rolls at points between the grooves and little or no grip is applied to the remaining filaments whereby successive sections of the tow across its direction of movement are gripped and released.

6. Apparatus as set forth in claim 4 in which said stationary guide bar means and said grooved roll are grounded.

7. Apparatus as set forth in claim 6, in which said grooved roll is circumferentally threaded and electrically grounded, and said stationary guide bar means is electrically grounded.

8. In the process in which a band of a crimped tow comprising about 500 to 1,000,000 continuous crimped filaments, having about 3 to crimps per inch and having crimps in registry, is opened and deregistered by passing it to the nip of a pair of rolls, one of which has a smooth rubbery insulating surface, said .rolls moving at a peripheral speed faster than the speed of said tow, and said tow leaving said nip is passed through an air-spreading zone in which the tow is confined between two parallel walls, one opposite each face of the tow band, while it is subjected to air streams issuing from at least one of said walls across the whole width of said tow, the improvement which comprises feeding said tow to said nip so that the tow makes sliding engagement with said moving smooth surface at a substantially constant angle substantially before it engages said nip.

9. In the process for opening a band of crimped tow comprising about 500 to 1,000,000 continuous crimped filaments, having about 3 to 80 crimps per inch, a denier per filament of about 1 to 25, carrying about 0.2 to 0.5% of an insulating silicone finish substantially free of antistatic agents, and having crimps in registry, by passing said tow band between a pair of rolls rotating at a controlled speed and then between a second pair of rolls rotating at a peripheral speed about 1% to 1% times the peripheral speed of said first pair of rolls, one of the rolls of said second pair of rolls being grooved circumferentially and the other having a smooth electrically insulating surface, the improvement which comprises passing the tow in the reach between said pairs of rolls in contact with a stationary guide so positioned that the straight line from the guide to the nip of said second pair of rolls intersects a portion of said smooth-surfaced roll so that the tow is in sliding engagement with a substantially constant arc of the moving smooth surface of said roll substantially before it passes through said nip.

References Cited UNITED STATES PATENTS 2,843,881 7/1958 Bishop et al. 19-65 3,032,829 5/1962 Mahoney et al 1965 3,046,632 7/ 1962 Tsutsumi 281 MERVIN STEIN, Primary Examiner. DONALD W. PARKER, Examiner. D. NEWTON, Assistant Examiner. 

1. IN THE PROCESS IN WHICH A BAND OF A PLURALITY OF CONTINUOUS CRIMPED FILAMENTS HAVING CRIMPS IN REGISTRY IS OPENED BY PASSING SAID BAND THROUGH AN OPENING ZONE IN WHICH SAID BAND IS SUBJECTED TO THE ACTION OF A PATTERNED ROLL TO DEREGISTER SAID CRIMPS THROUGH RELATIVE MOVEMENT OF SAID FILAMENTS UNDER THE INFLUENCE OF SAID PATTERNED ROLL, THE IMPROVEMENT WHICH COMPRISES PASSING SAID BAND IN SAID ZONE IN SLIDING CONTACT OVER AN ELECTRICALLY INSULATIING SURFACE. 